The present invention relates to tubular conduits of the type adapted and used for transporting a traveling textile yarn or the like from one location to another.
Over recent years, it has become an increasingly widespread practice in the textile industry throughout the world to utilize tubular conduits to transport textile yarns from one location to another in order to shield the yarn to prevent the accumulation of lint thereon as well as to prevent the release of fibrous lint therefrom into the ambient atmosphere. Furthermore, in operations requiring the simultaneous transportation of a plurality of yarns, the use of a separate tubular conduit for each yarn readily facilitates the compact and organized handling of the traveling yarns without entanglement therebetween. For instance, one situation in which tubular conduits of this type have been widely used is the feeding of plural yarns from a creel supporting a plurality of yarn packages to a textile machine utilizing the yarns, e.g., a circular knitting machine. Co-pending U.S. patent application Ser. No. 598,266, filed Apr. 9, 1984, now U.S. Pat. No. 4,540,138 for a Textile Yarn Creel discloses such a use of yarn transporting tubular conduits. Typically, the tubular conduits utilized are ordinary small-diameter flexible nylon or other plastic tubing which is readily available and advantageously facilitates bending or curving of the conduit into various curvi-linear conditions to define a desired yarn traveling pathway.
In most yarn transporting operations, such tubular conduits operate very satisfactorily. However, problems of unacceptably high yarn tension and even yarn breakage have been encountered throughout the textile industry in attempting to utilize such tubular conduits for transporting polyester and some other synthetic yarns, particularly such filament yarns. In certain instances, the problem has been considered so acute that the use of tubular yarn transporting conduits has been abandoned altogether. One obstacle to the solution of this problem is that there does not seem to be any consensus within the textile industry as to the cause of this problem. Some persons theorize that the necessarily resulting frictional interaction between the polyester or other synthetic yarn and the nylon or other synthetic tubing creates a progressively increasing static electrical charge within the tubing which creates the undesirably high yarn tension and may ultimately cause yarn breakage. On the other hand, other persons believe that the polyester or other synthetic yarn tends to progressively wear and abrade the otherwise smooth interior surface of the tubing to the extent that ultimately friction between the yarn and tubing causes the yard tension and breakage problems. While either or both of these theories may be correct at least in part, the applicant has also discovered that variations in the amount of lubricating "coning" oil ordinarily placed on polyester and other synthetic yarns in finishing affects friction between the yarn and the tubing and particularly that an excess of the oil can unexpectedly produce an increase, rather than decrease, in yarn tension and breakage, indicating that excess oil increases friction between the yarn and the tubing.
Irrespective of the precise actual explanation for the cause of this problem, it appears that frictional interaction between the yarn and the tubing is at the root of the problem. In order to reduce friction, some textile equipment manufacturers have begun providing tubular conduit systems particularly designed for polyester and other synthetic yarns, utilizing only linear tubular sections angularly joined with one another by short connecting elbows. Presumably, frictional contact of any substantial extent between the yarn and this tubing system occurs primarily at the elbows, but not in the linear sections, whereby the overall amount of frictional contact between the yarn and the tubing system is reduced. While such tubing systems seem to experience fewer yarn tension and breakage problems in handling polyester and other synthetic yarns, such tubing systems must be specially constructed and dimensioned for each individual application and are more costly due in part to the necessary use of the elbow-type connectors and due as well to the increased assembly time and labor required to interconnect and set-up the linear tubular sections and the connecting elbows. Ordinary flexible tubing is considered much more desirable to use in that it can be readily bent and flexed to assume curvi-linear configurations to accommodate any particular yarn transporting requirement.
In contrast, the present invention provides an improved tubular conduit of a flexible character adapted for assuming curvi-linear conditions in generally conventional manner and specially provided with a novel interior wall configuration effective to substantially reduce frictional contact between the traveling yarn and the tubular conduit.